Inspired by a helpful UK product guide. This walk-through draws on "Repairing concrete paths and drives with Rizistal Deep Fill Repair Mortar", produced by UK concrete repair specialist Rizistal. Their demonstration is useful on the bonding agent step — a stage that is easy to skip but that makes the difference between a repair that lasts and one that falls out again by next spring.
1. Assess the damage and prepare your materials
Look at what you are dealing with. Hairline cracks that are structurally sound can be filled with a simple surface repair mortar. Crumbling edges, potholes, and delaminated surface (where the top layer has lifted away from the base) need a deeper repair. Large sections that have sunk or heaved are a different job entirely — that is usually a sub-base problem.
For surface damage up to about 50 mm deep, a ready-mixed concrete repair mortar is the right product. Bags are available from builders’ merchants and most DIY stores. Get more than you think you need — waste from mixing is inevitable.
2. Cut back to sound concrete
Do not try to repair over crumbling or loose material. Use a cold chisel and club hammer (or an angle grinder with a diamond disc for larger areas) to cut back the repair area until you reach solid concrete that does not flex, crumble, or delaminate when you tap it.
Aim for clean, vertical edges around the repair — a feathered edge (sloping to nothing) will not bond and will crack away again quickly. Undercut the edges slightly if you can, so the repair locks in mechanically as well as chemically.
3. Clear all dust and debris
Brush out loose material thoroughly with a stiff brush. Compressed air is ideal if you have a compressor; a leaf blower works too. You need a genuinely clean surface — dust and grit between the repair mortar and the base prevents proper bonding and is the number one cause of repair failures.
Dampen the repair area with clean water. You want the concrete damp but not puddled — a dry substrate draws moisture out of the mortar too fast, weakening it.
4. Apply a bonding agent
This step is skipped more often than it should be. A concrete bonding agent (SBR bonding liquid is a common UK product) painted into the repair area significantly improves adhesion between old and new concrete. Brush it on, work it into the surface, and allow it to become tacky before you apply the mortar — usually around 15–20 minutes depending on temperature.
Some repair mortars have bonding additives already included. Check the bag instructions before buying separate bonding agent.
5. Mix and apply the repair mortar
Mix the mortar according to the manufacturer’s instructions — most ready-mixed products just need water added, a little at a time, until you reach a stiff, workable consistency. It should hold its shape when you form it with a trowel but not be crumbly or sticky.
Press the mortar firmly into the repair, compacting it as you go to remove air pockets. For deep repairs (more than 30 mm), apply in two layers and allow each to firm up before adding the next. Overfill the repair very slightly — you will screed it back level in the next step.
6. Level and finish the surface
Use a steel float or a straight piece of timber to screed the mortar flush with the surrounding path. A very light stipple with a brush will match the texture of the original concrete and reduce the visual contrast of the repair. If the path has a specific texture, match it while the mortar is still green.
To be fair, new concrete mortar never perfectly matches old weathered concrete in colour. It lightens as it cures and will fade further over a few seasons outdoors. Worth knowing before you worry about it looking different on day one.
7. Protect the repair while it cures
Keep the repair damp for the first 24–48 hours: mist it with water a couple of times if the weather is dry and warm. In hot sun, cover it with damp hessian or polythene to prevent the surface drying too fast and cracking. In freezing conditions, cover with insulating material — new concrete repairs should not be exposed to frost until they have cured for at least 48 hours.
Keep foot traffic off for 24 hours and vehicle traffic off for at least 72 hours.
8. Seal the finished repair (optional)
A penetrating concrete sealer applied to the finished, cured repair protects it against frost and reduces water absorption — which is the main cause of long-term concrete deterioration. It also brings some uniformity to the colour difference between old and new concrete. Not essential, but worth doing on a path that gets heavy rain or frost exposure.
When to call a handyman
Call Richard if the path has sunk, heaved, or cracked through the full depth — that needs sub-base work, not surface repair. Also call if the area is large, the edges are too degraded to cut cleanly, or if you have a lot of paths and drives that all need attention at once. Concrete repair is satisfying work when the repair area is well defined. Less so when it is not.
Need path or driveway repairs in East Kent?
The Sandwich Handyman handles concrete and masonry repairs, path work, and property maintenance in Sandwich and nearby villages.
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